1. Field of the Invention
The present invention relates to a single-facer to be equipped in a corrugating machine, and more particularly to a sticking mechanism between a core paper web and liner, a pitch circle diameter ratio between upper and lower corrugating rolls, and regulation of a surface temperature of a single-faced corrugated cardboard sheet in the single-facer.
2. Description of the Prior Art
At first, description will be made on general constructions and operations of heretofore known single-facers with reference to FIGS. 6, 7, 8 and 9. FIGS. 6 and 7 illustrate general constructions of belt-pressing type single-facers in the prior art, and FIGS. 8 and 9 are schematic views showing meshing conditions between upper and lower corrugating rolls having the same pitch circle diameters in the prior art for explaining disadvantages of such single-facers in the prior art.
As shown in FIG. 6 or 7, in a belt-pressing type single-facer in the prior art, after paste was applied via a paste application roll 16 to crest portions of corrugations of a core paper web 3, which was corrugated into a wave-shape by passing through a gap between upper and lower corrugating rolls 1 and 2 meshed with each other, the core paper web 3 and a liner 5 fed through another route are joined together, and by applying a pressing force to the joined web and liner at a predetermined temperature, a single-faced corrugated cardboard sheet 6 is produced. As pressing means necessitated for sticking the above-mentioned raw paper webs (core paper web and liner paper web), a part of an endless belt 7 is brought into contact with the liner 5, and a pressing force is generated by means of only a tension of the belt 7. By the way, in the case of sticking the corrugated core paper web 3 with the liner 5 via the applied paste, as a necessary condition, besides the above-described proper temperature and pressing force, a predetermined pressing time is necessitated, and in order to achieve preferable sticking, among these temperature, pressing force and pressing time, there exists a correlating condition to be fulfilled. In other words, if the above-mentioned pressing force is increased, the pressing time can be shortened, and if the pressing time is extended, then the pressing force can be reduced. In addition, even if the paste is heated and its temperature is raised, also the pressing time can be shortened. To that end, a single-facer constructed in such manner that a part of the rolls wrapped with the endless belt 7 can be moved and thereby a tension of the belt as well as a wrapping angle .theta. of the belt around the corrugating roll can be arbitrarily varied, has been heretofore proposed.
A single-facer illustrated in FIG. 6 is constructed in such manner that a part 8b of a roll pair 8 having an endless belt 7 wound therearound can be moved in the tangential direction of the belt with respect to a downstream side corrugating roll 1, so that by appropriately regulating a hydraulic pressure (or pneumatic pressure) applied to a cylinder 12, a tension of the endless belt 7 can be controlled and thereby a pressing force generated between the belt 7 and the upper corrugating roll (downstream side roll) 1 having the belt 7 held in contact therewith can be regulated.
While, a single-facer illustrated in FIG. 7 is constructed in such manner that a part 8b of a roll pair 8 having an endless belt 7 wound therearound can be moved in the vertical direction via a cylinder 12, so that by varying relative positions between the roll 8b and the upper corrugating roll (downstream side roll) 1, a wrapping angle .theta. of the endless belt 7 around the above-mentioned corrugating roll 1 can be regulated.
However, in the single-facers illustrated in FIGS. 6 and 7, although regulation of a pressing force and a pressing time is possible, there still remained a shortcoming that there was no regulating means for maintaining a sticking force between corrugation crest portions of the core paper web and the liner constant, and so control was difficult.
Next, description will be made on shortcomings of the corrugating roll section in the single-face in the prior art. As illustrated in FIGS. 8 and 9, for the upper and lower corrugating rolls 1, 2 included in the heretofore known single-facers, generally corrugating rolls having their pitch circle diameters d.sub.1, d.sub.2 ; D.sub.1, D.sub.2 formed in the same size were combined, and therefore, speed-up of a manufacturing speed was structurally limited. More particularly, in the event that speed-up is contemplated by combining upper and lower corrugating rolls 1 and 2 having small diameters d.sub.1, d.sub.2 in the prior art as shown in FIG. 8, a press-pinching time becomes short, and so, there occurs the problem that sticking between the core paper web 3 and the liner becomes unreliable. Instead, if the diameters D.sub.1, D.sub.2 of the upper and lower corrugating rolls 1 and 2 are made large as shown in FIG. 9 in order to obviate the above-described shortcoming, then not only the entire apparatus becomes large-sized (H.sub.o &lt;H), but also a number of simultaneously meshing teeth increases (S.sub.o &lt;S), hence a tension applied to a core paper web 3 to be corrugated becomes large, and consequently, there occurs a disadvantage that the core paper web 3 would be torn. (The number of simultaneously meshing teeth is normally 3-4 teeth at the maximum.) As a counter-measure for resolving such problem in the prior art, while a single-facer of the heretofore known type but including a combination of corrugating rolls having different diameters, was manufactured, this single-facer did not have a construction (combination) taking a particular ratio of corrugating roll diameters into consideration, but it had a serious shortcoming that in the event that a tooth on the outer circumferential surface of a corrugating roll should be damaged due to biting of foreign matters or the like, that damage would be transferred to the entire circumference as a result of meshing of the corrugating rolls. In such single-facers of heretofore known type, various shortcomings were still left also in the corrugating roll section.
Although the single-facets illustrated in FIGS. 6 and 7 can regulate a pressing force via a belt and a wrapping angle (pressing time), respectively, as described above, regulator means for maintaining a sticking force between a corrugation crest portion of a core paper web and a liner constant, is not present, and so, it was not known to what extent a pressing force or a pressing time should be regulated for obtaining an optimum sticking force. Also, even if the pressing force regulating mechanism shown in FIG. 6 and the pressing time regulating mechanism shown in FIG. 7 were to be equipped in juxtaposition, it would be impossible to simultaneously regulate a pressing force and a pressing time, regulating ranges of a belt tension as well as a wrapping angle of an endless belt would become large, and control was very difficult. Besides, with regard to shortcomings of the corrugating roll section, since the upper and lower corrugating rolls are formed to have the same pitch circle diameter and combined, structurally it was impossible to employ large diameters, and hence, speed-up of a manufacturing speed could not be realized.